1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device for processing a substrate by a source gas obtained by vaporizing liquid source, and a substrate processing apparatus.
2. Description of Related Art
As a method of forming a thin film by atomic layer unit on a substrate such as a wafer, a so-called ALD (Atomic Layer Deposition) is used. In the ALD method, for example, (1) the step of supplying a first processing gas into a processing chamber in which the substrate is contained and making the first processing gas adsorbed on the surface of the substrate, (2) the step of introducing inert gas into the processing chamber to remove the first processing gas remained in the processing chamber and purging an inside of the processing chamber, (3) the step of supplying a second processing gas into the processing chamber and causing reaction to occur between the second processing gas and the first processing gas adsorbed on the surface of the substrate, and (4) the step of introducing the inert gas into the processing chamber for removing the remained second processing gas in the processing chamber and a reaction by-product and purging the inside of the processing chamber, are set as one cycle, and this cycle is repeated.
Here, as the aforementioned first processing gas, for example, gas obtained by vaporizing a liquid source, being in a liquid state at a normal temperature, is used in some cases. Then, as an apparatus for vaporizing the liquid source, a vaporizer is used in some cases. The vaporizer has a vaporizing chamber for vaporizing the liquid source and generating gas; a liquid source flow passage, being a flow passage for discharging the liquid source into this vaporizing chamber; and a supply port for supplying the source gas generated in the vaporizing chamber to outside.
Note that an open/close valve that controls supply of the liquid source is provided on the flow passage of the liquid source. Then, in the aforementioned step (1), by opening the open/close valve provided on the flow passage of the liquid source, the supply of the liquid source to the vaporizing chamber is started. In addition, in the step other than the step (1), the supply of the liquid source to the vaporizing chamber is stopped by closing the open/close valve, and in order to prevent the change in quality of the liquid source remained in the flow passage of the liquid source, thereby blocking the flow passage of the liquid source, the inert gas is supplied into the flow passage of the liquid source and the inside of the flow passage is purged.
Here, as the aforementioned liquid source, for example, an organic metal liquid source including elements such as Sr (strontium), Ba (barium), and La (lanthanum) is used in some cases. These organic metal liquid sources have low vapor pressure and high viscosity. Therefore, the aforementioned organic metal liquid source is diluted by, a solvent, for example, such as ECH (ethylcyclohexane) and THF (tetrahydrofuran) in many cases.
However, the aforementioned solvent has a higher vapor pressure than that of the organic metal liquid source functioning as a solute. Therefore, in the step other than the aforementioned step (1), when the inert gas is supplied into the liquid source flow passage and the inside of the flow passage is purged, only the solvent is previously turned into vapor, and only the organic metal liquid source remains in the flow passage of the liquid source in some cases. Then, since the organic metal liquid source has high viscosity, it is difficult to remove the organic metal liquid source, even if the inert gas is supplied into the flow passage of the liquid source and the inside of the flow passage is purged. Therefore, the inside of the flow passage of the liquid source is blocked by the liquid source in some cases.